In BI, you could do this:
• Create a new material and add a diffuse image texture to it (say a wood grain)
• Set that texture to influence the normal
• Assign the material to a plane and unwrap it
• Bake a normal map that would incorporate the influence from the diffuse
Is it possible to repeat this feat is Cycles? My efforts so far have failed – the geometry is of course reflected (fairly dull for a plane) but I cannot seem to find a way of incorporating the “bump” from the diffuse.